Basically high resilience polyurethane foams are produced by the reaction of highly primary hydroxyl-capped, high molecular weight polyols with organic isocyanates and water. High resilience polyurethane foams are distinguishable, in part, from conventional hot cure polyurethane foams by the use of such polyols and the fact that high resilience polyurethane foams require little or no oven curing and thus are often referred to as cold cure foams. Such foams are extremely desirable for cushioning applications because of their excellent physical properties, e.g., very high foam resilience, low flammability, open-celled structure, low flex fatigue (long life) and high SAC factors (load bearing properties).
Because of the high reactivity of high resilience foam ingredients and their rapid buildup of gel strength, sometimes the foam can be obtained without a cell stabilizer. However such foams typically have very irregular cell structure as particularly evidenced by surface voids and the lack of discovery of a proper agent to help control cell structure has been a major problem in the art.
Attempts to solve this problem with surfactants generally employed in the stabilization of hot cure polyurethane foam have not proven satisfactory because such surfactants tend to overstabilize, causing extremely tight, shrinking foam. Nor is the problem corrected by reducing the concentrations of such surfactants, since at concentrations required to eliminate shrinkage, the cells are no longer stabilized satisfactorily and the foam structure becomes irregular, coarse and contains surface voids.
U.S. Pat. No. 4,042,540 discloses that a variety of low viscosity siloxanes, including low viscosity dimethylsilicone oils, are better stabilizers for high resilience polyurethane foams than high viscosity dimethylsilicone oils. The use of low viscosity dimethylsilicone oils alone as stabilizers for high resilience foams also has various disadvantages. For example, at low concentrations they create metering and pumping problems in the processing of the foam, while at higher concentrations these oils adversely affect the physical properties of the foams. Such metering and pumping problems might be solved by using a low concentration of the silicone dissolved in a solvent. However, solvents for such dimethylsiloxane oils that are nonreactive with the foam ingredients e.g. alkanes, hexamethyldisiloxane, and the like, can adversely affect the foam's physical properties in proportion to their concentration and generally create flammability hazards. Furthermore, isocyanate reactive diluents, such as polyether triols and the like which do not significantly change the foam's properties, inasmuch as they react into the system and become part of the foam structure, are not satisfactory solvents for dimethylsilicone oils, since not enough oil can be dissolved to provide foam stabilization at practical solution concentrations. High resilience foams are also adversely affected by dimethylsilicones having more than about 10 dimethylsiloxy units per siloxane. For example only five or ten weight percent of such species in a dimethylsilixone oil can appreciably degrade the foam's physical properties and even cause foam shrinkage.
Several other patents disclose organosiloxane copolymers and their use as foam stabilizers in high resilience foam formulation. U.S. Pat. No. 3,905,924 relates to the use of cyanoalkylsiloxane copolymers as stabilizers for high resilience polyurethane foam. U.S. Pat. No. 3,741,917 describes siloxane-oxyalkylene copolymers and the use of said organosiloxane copolymers in the formulation of high resilience polyurethane foam. U.S. Pat. No. 3,935,133 teaches the use of high molecular weight silicate esters of polyether alcohols to stabilize high resilience polyurethane foam. U.S. Patent Application Ser. No. 932,637, filed Aug. 10, 1978 U.S. Pat. No. 4,210,726, discloses a process for producing high resilience polyurethane foam utilizing as a foam stabilizer a combination of an organosiloxane copolymer and a hydrocarbon oil. However, none of the above mentioned patents or applications disclose the novel alkyl-modified siloxane copolymers of this invention or their unexpectedly beneficial utility as foam stabilizers in the manufacture of low density high resilience polyurethane foam.
Within the past few years, cushions fabricated from high resilience polyurethane foam have gained increasingly wide acceptance in automotive seatings. Automotive industry requirements decreased the foam density needed for seat cushions, thus increasing the difficulty of stabilization of high resilience polyurethane foam. Recently new systems with high water levels have been proposed which can produce foam cushions with densities of 1.50 to 1.75 lbs./cubic foot and acceptable physical properties in comparison to the commercial foaming systems. However, without any foam stabilizing surfactant, the new high water systems produced foams with large and irregular cells or caused collapse of the foam. The addition of commercial high resilience polyurethane foam surfactants (including the low viscosity dimethyldilicone oils, cyanoalkylsiloxane copolymers and siloxane-oxyalkylene copolymers disclosed in the above-mentioned patents) to this new high water system did not correct these problems. The commercial high resilience polyurethanes foam surfactants caused collapse of the foams, and commercial flexible "hot-cure" polyurethane surfactants caused severe shrinkage and pneumatic foams. Thus, it remains a problem in low density high resilience polyurethane foam formulations to obtain a surfactant which has a proper degree of cell stabilizing ability.